diff --git a/t/t_string.c b/t/t_string.c
index defb738..313efd3 100644
--- a/t/t_string.c
+++ b/t/t_string.c
@@ -29,10 +29,9 @@
 
 #include "cryb/impl.h"
 
-#include <sys/types.h>
-
 #include <stddef.h>
 #include <stdint.h>
+#include <unistd.h>
 
 #include <cryb/string.h>
 
diff --git a/t/t_wstring.c b/t/t_wstring.c
index 214edb7..f3e5879 100644
--- a/t/t_wstring.c
+++ b/t/t_wstring.c
@@ -29,10 +29,9 @@
 
 #include "cryb/impl.h"
 
-#include <sys/types.h>
-
 #include <stddef.h>
 #include <stdint.h>
+#include <unistd.h>
 #include <wchar.h>
 
 #include <cryb/wstring.h>